Construction of Pt-Ni nanocomposites from Pt-Ni multinuclear complexes on gold(111) surface and their electrocatalytic activity for methanol oxidation

Novel electrocatalysts for methanol oxidation were prepared from two Pt-Ni multinuclear complexes, [Pt2{Ni(NH2CH2CH2S)2}4]Cl4 and [Pt(bpy){Ni(NH2CH2CH2S)2(bpy)}](NO3)2 (bpy = 2,2′-bipyridine). They were adsorbed on a Au(111) surface by immersing the Au(111) electrode in solutions containing these complexes. The modified Au(111) electrodes were then subjected to potential cycling or heat-treatment at 200 °C and 300 °C so that organic ligands were decomposed and adsorbed complexes were converted to nanocomposites. For a comparison, Au(111) electrode modified by a Pt based nanocomposite prepared by using a di-platinum(II) complex ([Pt2(terpy)2(μ-otdst)]2 + (terpy = 2.2′:6′,2″-terpyridine, H2otdst = 2-octylthio-4,6-disulfanyl-1,3,5-triazine)) as a starting molecule. The surface species were characterized by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) in addition to cyclic voltammetry (CV). Two-dimensional nanocomposites of monatomic height were observed by STM. The coverages of the nanocomposites were 2-8%. By repeating the complex adsorption and heat-treatment for five times, nanocomposites of higher coverage of 13-19% with monatomic height were formed on Au(111) surface. The resultant nanocomposites showed high activity for methanol oxidation reaction (MOR) with an improved CO-tolerance in a 0.1 M KOH aqueous solution containing 1 M CH3OH.